The present invention refers to a mixer for a multiple component dispensing cartridge or dispensing appliance, having at least two storage cylinders and comprising a mixer housing containing a mixer element group and being attachable to the dispensing cartridge or appliance, and an inlet section comprising side by side separate inlets communicating with the dividing edge of the first element of the mixer element group. Such mixers are known and they have the function of intimately mixing the components in order to prepare them for their application. For the sake of clarity, two components are mentioned only in the following description, but it is evident that there can be more than two components. The dividing edge is the first edge where the united material streams are first divided for being mixed together.
In the cartridge/mixer assemblies of the prior art, two or more material streams flow from the outlets of the cartridge to the dividing edge of the first mixer element of the mixer element group for subsequent thorough mixing. However, there is a problem of presenting the components in an optimal manner to the first dividing edge of the mixer element group depending upon the volumetric ratio of the components and their viscosities.
With mixing ratios higher than 1:1, e.g. 10:1, there is a likelihood that the larger component fills up part of the length of the mixer element group of the mixer at the beginning of the dispensing process and that the second component, having a smaller volume, is thus suppressed or subdued. In the inlet area in particular, the larger partial flow "A" will press the smaller partial flow "B" against the wall of the mixing tube on the "B" side where it is held back by wall friction and therefore subdued or suppressed by the larger "A" component. Thus the mixing process can only begin with some difficulty and delay. In this initial phase, the partial flow "A" precedes and a proper mixture cannot be achieved in the correct volumetric ratio. Thus the components cannot properly react with each other, resulting in defective bonds, seals, joints, impressions, etc. Since the "B" component is generally a hardener or catalyst, a mixture with an insufficient amount of "B" component is useless, and, because of this in order to stabilize the desired proportions of the components, it is common practice to dispense and discard a certain quantity of material before being able to start the proper application of the mixture. Besides waste of material, the initially dispensed material may not harden and may additionally cause disposal problems. If used, however, it may cause end product failure.
In U.S. Pat. No. 5,487,606 of the same applicant, a solution to this problem is suggested by first retaining the larger "A" component in a chamber and by providing means for directing it to the inlet chamber of the second "B" component for carrying the latter along. Although this embodiment provided an improvement with respect to the then state of the art, it results in an increased flow resistance due to several necessary restrictions of the cross-sectional area which requires higher dispensing forces and may possibly make reinforcement of the cartridge walls necessary.
In the mixer according to U.S. Pat. No. 5,498,078 of the same applicant, the intimate mixing of the components has been improved yet further over the then existing prior art. Also in this disclosure, as in the aforementioned, the components are brought together substantially in the direction of the longitudinal axis of the mixer.